Question

which of the following are equations?
check all that are true.

• □ $3 + 4 = y$
• □ $9/z = 5$
• □ $7 + y$
• □ $3(a + 2a) = 18$
• □ $=$

Explanation:

Step1: Recall the definition of an equation

An equation is a mathematical statement that shows the equality of two expressions, and it contains an equal sign (\(=\)) and at least one variable (in most cases of algebraic equations).

Step2: Analyze each option

• For \(3 + 4=y\): It has an equal sign and the variable \(y\), so it is an equation.
• For \(\frac{9}{z}=5\): It has an equal sign and the variable \(z\), so it is an equation.
• For \(7 + y\): It does not have an equal sign, so it is not an equation (it is an expression).
• For \(3(a + 2a)=18\): It has an equal sign and the variable \(a\), so it is an equation.
• For \(=\): It does not have two expressions to show equality (no expressions on either side of the equal sign), so it is not an equation.

Answer:

• \(3 + 4 = y\)
• \(\frac{9}{z}=5\)
• \(3(a + 2a)=18\)